Sanofi Pasteur has reported promising results from a trial of its vaccine against H5N1, the strain of bird flu which has killed at least 69 people in Asia since 2003 and is a candidate to cause a flu pandemic.

The 300-patient trial showed that two 30mcg doses of the vaccine, given along with an adjuvant (alum) to increase its efficacy, produced an immune response comparable to that achieved with current vaccines used to protect against seasonal flu.

Sanofi Pasteur, the vaccines business of Sanofi-Aventis, said that this is the first trial of an H5N1 pre-pandemic influenza vaccine candidate that compared vaccines with and without adjuvants. The finding is important because it means that lower doses of antigen could be used in vaccination programmes, boosting the number of doses that could be produced from each production run.

The data will be submitted as part of the company's core vaccine dossier to the European Medicines Agency (EMEA). In October, the agency put in place a fast-track system to accelerate the approval process for pandemic flu vaccines. It involves filing partial data on a potential vaccine which could be updated quickly once the actual strain causing a pandemic has been identified.

Sanofi Pasteur said it will now scale up its production for the H5N1 vaccine to mimic manufacturing process that will be used during a pandemic, and conduct clinical trials on this version to make sure it behaves in the same way.

A number of other companies are working on the development of pandemic flu vaccines, in most cases based on the H5N1 strain. They include GlaxoSmithKline, Chiron, Akzo Nobel, MedImmune and Baxter International.